1. Field of the Invention
The invention is concerned with a novel group of compounds and their use as friction reducing and antioxidant additives in lubricants, i.e. lubricant compositions containing same.
2. Description of the Prior Art
It is known that sliding or rubbing metal or other solid surfaces are subject to wear under conditions of extreme pressure. Wearing is particularly acute in modern engines in which high temperatures and contact pressures are prevalent. Under such conditions, severe erosion of metal surfaces can take place even with present generation lubricants unless a load carrying or antiwear additive is present therein.
Friction is also a problem any time two surfaces are in sliding or rubbing contact. It is of especial significance in an internal combustion engine, because loss of a substantial amount of the theoretical mileage possible from a gallon of fuel is traceable directly to friction.
Borate esters of hindered phenols, i.e. phenols in which both ring positions ortho to the hydroxy group have been substituted by bulky hydrocarbyl groups, are known in the art. U.S. Pat. No. 3,347,793, for example, discloses lubricants containing compounds made by reacting a hindered phenol, e.g., 2,6-di-tert-butyl-p-cresol, with a borate ester. Similarly, U.S. Pat. No. 3,356,707 and U.S. Pat. No. 3,359,298 disclose lubricants containing a product made by reacting a 2,6-tertiary alkyl phenol with a boron compound (e.g., an alkyl borate) to produce a hindered phenol borate ester. The additives are taught to be hydrolytically stable and to possess antioxidant properties. The hindered phenyl borate esters of this invention are believed to be unknown.